Surface morphology and pervaporation performance of electric field enhanced multilayer membranes

Polyethylenimine/poly(acrylic acid sodium salt) (PEI/PAA) ultrathin polyelectrolyte multilayer membranes were fabricated by an electric field enhanced method and were used for isopropanol/water pervaporation. Surface properties of the electric field enhanced multilayer polyelectrolyte membranes (EPEMs) prepared under different conditions were investigated by atomic force microscopy (AFM) and contact angle (CA) measurements. It was found that surface properties (roughness and hydrophilicity) of EPEMs strongly depend on the direction of the electric field, dipping time, applied voltage, number of bilayers, which, in turn, affect their pervaporation performance. The (PEI/PAA)4PEI EPEMs fabricated with a dipping time of 15 min and an applied voltage of 5 V for separating 10 wt% water–isopropanol mixtures exhibited high separation factor and large flux. Meanwhile, the performance of the EPEMs displays good storage stability within 60 days.